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Department of EnergyWashington, DC 20585

October 2. 1996

The Honorable John T. ConwayChairmanDefense Nuclear Facilities Safety Board625 Indiana Avenue, NWSuite 700Washington, D.C. 20004

Dear Mr. Chairman:

Enclosed is the “Evaluation of the Safety Merits and Demerits ofUsing Privately Operated Facilities for Disposal of the Departmentof Energy (DOE) Low-Level Waste” report dated September 1996.This document is a deliverable due to you as detailed in SecretaryO’Leary’sApril 1996, Implementation Plan for Defense NuclearFacilities Safety Board Recommendation 94-2, task IV.B.4. Thisreport was developed as part of the Systems Engineering task forlow-level waste management.

This report evaluates safety issues associated with low-levelwaste disposal at privately operated facilities versus DOE managedfacilities. Further, the Privatization report will be used toestablish guidance and criteria for sites to use when consideringdisposal options. Based on conversations with your staff, thisguidance and criteria (specified as part of the Task IV.B.4deliverable) will be part of the Low-Level Waste ProgramManagement Plan deliverable.

Sincerely,

&4La

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Alvin L. AlmAssistant Secretary for

Environmental Management

Enclosure

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EVALUATION OF THE SAFETY lMERITS AND DEMERITS OF

USING PRIVATELY OPERATED FACILITIES FOR DISPOSAL OF

DOE LOW-LEVEL WASTE. .

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September 1996

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Evaluation of the Safety Merits and Demerits of Using Privately Operated Facilities for

Disposal of DOE Low-Level Waste

prepared by

Robert WatersWu-Ching Cheng

Sandia National Laboratories

and

Joanne SteingardBDM Federal

September 1996

Prepared for theU.S. Department of Energy

Assistant Secretary for Environmental ManagementUnder Contract DE-AC04-94AL85000

TABLE OF CON’TENTS

EXECUTIVE SUMMARY ............................................................................................................INTRODUCTION .......................................................................................................................... ;

Background ................................................................................................................................. 1Purpose ......................................................................................................................................... ;Approach .................................................................................................................... .................. ~

COMPARISONS BY FUNCTIONAL A~AS ............................................................................. 5Sitirw .. .. .........................................................................................................................................>

Surrounding Environment ............................ ............................................................................. 6Disposal Facility- Design ................................................................................................ ........ . (,

Waste Foci ............................... ............... ...... ......................................................... ................. :

Llmmng Inventories .................... ... ..............................~.......................................................... ?

Summary Comparison of DOE and Privately Operated Facilities - Siung .............................. 8Des]gn. ........................................................................................................................................... Q

Performance of Facility Design for the Water Pathway ......................................................... i 1Performance of Facility Design for Intrusion vs. the Water Pathway .................................... 14Summary Comparison of DOE and Privately Operated Facilities - Design ..............’............. 15

Operations .................................................................................................................................. 16Actwity Tracking Systems ...................................................................................................... 17Waste Classification System..." ................................................................................................ 17Summary Comparison of DOE and Privately Operated Facilities - Operations ..................... 1!3

Closure ....................................................................................................................................... 19Regulatory Guidelines ............................................................................................................ 19Proximity of Disposal Area to Property Boundq ................................................................ . 20Summary Comparison of DOE and Privately Operated Facilities - Closure .......................... 21

Waste Forms .............................................................................................................................. zz

Waste Forms Accepted at LLW Disposal Facllities ............................................................... 22Physical Requirements for Waste ........................................................................................... Z3Performance for Grout. Polyethylene Microencapsulation. and Glass ..................... .............. 23Sites and Radionuclides that May Benefit From Enhanced Waste Forms ............................. 24Summary Comparison of DOE and Privately Operated Facilities - Waste Form ..................25

Performance Assessment ~7............................................................................................................ .Limiting Concentrations -)7........................................................................................................ .Summary Comparison of DOE and Privately Operated Facilities - PA ........~........................ 29

Approval and Oversight ............................................................................................................. 31Approach Used by NRC and Agreement States ..................................................................... 31Approach Used by DOE ................................. ...................................................................... :1Summary Comparison of DOE and Privately Operated Facilities-Approval and Oversight .32

CONCLUSIONS ........................................................................................................................... 34REFERENCES ............................................................................................................................. 35

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LIST OF FIGURES

1 Perrmssible waste concentrations (~Ciim3) for the water pathwa}. ....................................... 152 Penmssible waste concentrations (pCi/m3) for the trench and tumulus designs for the

standard intrusion scenaios . ................................................................................................... I-!

LIST OF TABLES

1 Facility Designs Used at LLY$’Disposal Sites (Cole et al., 1995) . ........................................... ? ‘2 Characteristics of the Indicator Radionuciides ..............i .........................................................l0~ A General Grouping of the 58 Radionuclides Evaluated in the PE (from DOE. 1996a) ........ 11-.J Reiati\e Retention Performance of Waste Forms Normalized to Grout Perfomlance ~frorn

SNL. 1996) ?4.............................................................................................................................. -5 Concentration Limits (~Ci/m;) for Radioactive Constituents at Commercial and DOE

Disposal Sites ~assuming waste bulk density of2.4 g/cm3) .................................................... 27

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EXECUTIVE SUMMARY

One of the tasks delineated by the Defense NucIear Facilit y Safety Board in itsRecommendation 94-2 was an evaluation of privately operated facilities for disposal ofDepartment of Energy (DOE) low-level waste (LLW). The safety merits and demerits ofusing private disposal facilities (e. g.. Envirocare and Barnwell) compared to disposing otLL W at DOE facilities have been evaluated using a systems approach based on se}entimctional areas: siting, design. operations. closure, waste form. performance assessment. andapproval and overs@m

~ Privately operated LLV’ disposal facilities licensed by the Nuclear RegulatoryCommission (_NRC) or NRC Agreement States musx meet the siting requirements of 10 CFRPart 61. Generally. the siting process begins with an entire state. and screening criteria areapplied to arrive at the potential disposal locations. Detailed site invesngations areperformed at the selected site to provide data to evaluate its suitability and identifj anj’restrictions on wastes that must be imposed. The siting requirements for DOE disposalfacilities are contained in DOE Order 5820.2A. The DOE selects sites for its disposalfacilities from within the boundaries of its reservations. Similar to commercial sites.permissible inventories of radionuclides for disposal are based on performance assessmentsthat consider the design of the proposed disposal facility, the final form of the disposedwaste. and the surrounding environmental conditions.

-. Both Privately operated and DOE-managed disposal facilities generally use shallowtrenches in arid regions of the country and tumulus or vault designs in humid regions of thecotint~. The prima~ advantage of the more engineered designs such as the tumulus or vaultIS for disposal of wastes containing shorter-lived radionuclides: for a water pathway to thecompliance point. these radionuclides are detained longer in the disposal facility and decaj’ tolow levels while migrating through the environment; for inadvertent intrusion, theseradionuclides have an opportunity to decay to low levels because the more-engineeredfacilities are assumed to deter intrusion for longer periods of time.

~. privately operated disposal facilities segregate waste for disposal according tothe NRC’s waste classification system. This classification” system is considered whendeveloping the waste acceptance criteria (WAC) for privately operated facilities. The DOEalso bases its WAC on site-specific performance assessments and safety analysis reports.although it does not use a waste classification system. For both privately operated and DOE-

managed facilities, radiological limits vary from site to site based on the capability of thenatural and man-made features incorporated into the design.

-. privately operated disposal facilities are required to have a closure plan as part ofthe application for a license. The snes are located on land leased from a state or federalentity, and the site returns to that government entity upon meeting all closure requirements,.

including a surety bond for any necessary future remedial action. The DOE may take controlof these lands if requested by the controlling government entity. The DOE disposal facilitiesare located on federally controlled reservations, and long-term control is provided by DOE.

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Closure plans for these facilities are also reqwred but have not been de~feloped by the sites t~~serve as input for performance assessments: assumptions about the final closureconfiguration are contained in the performance assessments. This issue is addressed m thecorrective action plans developed 10 resolve vulnerabilities identified in the ,complex-widereview of the LLIJ’ system conducted as part of DOE’s implementation plan for

Recommendation 94-2.

The large sizes of the DOE reservations generally will provide more protection to thepublic than the privately operated sites. although the disposal facilities at the Oak RidgeReservation. which are located near the reservation bound~. are a notable excepuon.

~as[e ~. rm. The primary purpose of waste forms for disposal of LL~’ is to pro~ride stabilit! ~‘ ~for the disposal facility. AI1 LLW disposal facilities have requirements to ensure stability ofwaste based on compressive strength of the waste or package and mmlmized void space.W-asle forms can also ald in nlmimlzlng releases of radionuclides to the en~qronmenl.

Facilities in humid regions of the count~ benefit most from this aspect of waste forms due tothe higher potential infiltration rates at these sites. In all en~rironments. enhanced wasteforms may be important in deterring inadvertent intrusion by allowing the intruder torecognize the waste as a hazard. As with more-engineered disposal facilities. more-engmeered waste forms are important primarily for shorter-lived radionuclides: longer-livedradionuclides will not decay appreciably while being retained within more durable wasteforms. “ “

Performance Assessment. The assessment methodologies used to analyze performance ofcommercial and DOE LLW disposal facihtles are similar. However, the differences inconservatism used by the analysts for the site-specific assessments may be very different.The performance assessments result in site-specific concentration limits, which are used todevelop WAC for the disposal facility. The concentration limits for radionuclides atBarnwell and SRS are generally similar for most radionuclides. However. at Barnwell. thelimlts for tritium and Tc-99 are two and three orders of magnitude higher than those for thenearby DOE SRS. indicating that the performance assessment for SRS is more conservativethan that at-Bamwell for releases to the environment. The Iimlts at Envirocare are generallyequivalent to the NRC Class A limits. There are no site-specific limits on radionuclideconcentrations in LLW at the Nevada Test Site (’NTS).

ADDrOVaiand Oversi ~. All privately operated disposal sites must meet the requirementsspecified by the NRC in 10 CFR Part 61 and those specified by the Agreement State. Theserequirements include obtaining and opera~ing under a license, submitting to periodiccompliance reviews and appraisals. and maintaining the financial capability to pay for anyfuture remedial activities. The operator is licensed and monitored by an external,independent government organization. S,ites controlled by the DOE are required to submitsite-specific radiological performance assessments and composite analyses. as well as safetyanalysis reports and other documentation to DOE headquarters for review and approval.

Oversight and compliance reviews are conducted by DOE’s Office of Environment. Safety,and Health (EH), which is a separate office within the department from the Office of

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Environmental Management (EM) that has programmatic responsibility over the LLY4’disposal facilities. Although EH and EM are fi,mctionally independent within the department.they both report to the Secretary of Energy. Outside of DOE, this fictional independencemay not be readily apparent. The DOE”s self-regulaung policy is perhaps the largestdifference between privately owned and DOE-owned disposal sites related to approval andoversight.

CON~l.USIONS. .

.. Althoughthe requirements and practices for privately operated and DOE-managedfacilities often differ within the seven xunctlonal areas. the resulting Ievei of protection “provided by the aggregate of these fimc[lonal areas are similar fcir both systems. Thesimilarity in approaches of DOE and NRC IS not surprising because both orgamzationsevolved from the same parent orgamza~ion and have continued close communication abou~

waste disposal.

However, in practice some differences are worth noting:

. The concentration limits at Barnweil for highly mobile radionuclides (e.g., tritium andTc-99) are two and three orders of magnitude higher than at DOE’s SRS. The disposalfacilities at both sites are vaults, and the primaqr difference appears to be due to thedifferences in conservatism used in the analysis of releases to groundwater.

● In some instances. the DOE Orders have not been implemented as intended. Forexample. the requirement for the development of closure plans was not always beingfollowed by the DOE sites. This deficiency IS now being addressed in the correctiveaction plans for the complex-wide review of DOE-S LLW system. which was conductedas part of the DOE Implementation Plan for Recommendation 94-2. Implementation ofplans to resolve other deficiencies ident~fied in Recommendation 94-2 is also proceeding,

● The siting requirements of NRC and DOE are similar: however, one major difference isapparent. While privately operated facilities are sited on property specifically. selected forthe purpose of LLW disposal. DOE is limited to selecting locations from within theboundaries of the reservations under NScontrol. In general, the locations for thesereservations were selected for reasons other than for their suitability for disposal of LL W,although. in general. suitable locations for disposal have been found at these sites.

● Privately operated facilities use the NRC waste classification system to determine thetype of packaging and waste segregation required for waste being disposed of at a site.DOE has chosen not to use such a system. relying instead site-specific performanceassessments to determine waste acceptance criteria. Both systems are sufficientlyprotective.

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INTRODUCTION

A qualitative and quantitative comparison of the approaches for disposal of Io\v-levelwaste (LL\~) used for privately operated facihties licensed by the Nuclear Regulato~Commission (NRC) or NRC Agreement States and used for Departmen~ of Energ~ ~DOE)-managed facilities developed under DOE Order 5820.2A is contained in this report Thiscomparison identifies the safety merits and demerits of using private facilities for disposal ofDOE LLW relative to using DOE-managed disposal facilities. Comparisons are made usinginforrnauon and data related to currently operating DOE and private disposal facilities.

.Analyses based on generic disposal facilities result in comparing the requirements in “the NRC regulations and the DOE orders. This type’ of comp=ison has recently been madeas a deliverable to the Defense Nuclear Facilities Safety Board (DNFSB ) pursuant to itsRecommendation 94-2 (Cole et al.. ! 995). This report builds on the work of Cole e~al. toevaluate the effects resulting from the differences m requirements of NRC and DOE.

Currently. two privately operated sites. Envirocare of Utah and Bamwell m SouthCaroIina. accept DOE LLW. The DOE’s six operating LLW disposal sites are Hanford inWashington s~ate. the Nevada Test Site INTS), the Idaho National Engineering Laborato~(INEL). Los .Mamos National Laboratory (LANL) in New Mexico, the Oak Ridge .Reservanon (ORR) in Temessee. and the Savannah River Site (SRS) in South Carolina.

Background

The fimdamental approaches to regulate and manage disposal of LLW now used byNRC and DOE are a result of the lessons learned from the early commercial disposalfacilities m the 1970s.’

Early commercial sites for LLW disposal (Beatty, Nevada; Maxey Flats, Kentucky;West ~:alle~. New York; Richland. Washington; Sheffield, Illinois; and Bamwell, SouthCarolina ~used shallow-land disposal .(INEL, 1994). a practice that was commonly used at thetime at the national laboratories involved in defense programs and atomic energy” research.Shailo\v-iand disposal was used near the point of waste generation. thereby reducingtransportation costs. The strategy underlying shallow land disposal was that the naturalcharacteristics of the earthen material would be sufficient to slow the movement ofradionuclides until they decayed to background levels. The strategy, however, presupposedthat disposal site locations would be selected that provided these kinds of natural barriers,that the form of the waste would not allow for easy release of radionuclides, and that disposalfacility operations would not reduce the safety of the system.

The significant problems leading to radionuclide migration were site instability anddifficulties in surface water and groundwater management (INEL, 1994). The instability ofthe sites also made prediction of long-term performance difficult. Experience at these sitesindicates that a combination of unstable waste forms, specific site characteristics, and certaindesign and operational practices led to problems with water management and site instability.

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Inadequate waste forms was a significant factor leading to failures at 3 (Maxe} Flats.Sheffield, and West Valley) of the 6 early commercial disposal sites (INEL. 1994). Becausewaste disposal was inexpensive. there was little incentive for waste generators to minimize

the amount of waste produced or to compac[ the material into a more stable waste form.Waste material degradauon and compression. which were accelerated b} contact with ~va~er.

led to senlement of the trench contents and subsidence or slumpmg of the trench co~ers.which in turn routed surface water mto the disposal trench and accelerated the degradation “cycle.

EariJ operating practices also contributed to rapid \vaste degradation. subsequentslumpmg of the trench covers. and the entry of water into the disposal units: Waste wasplaced within the disposal trenches with llttle or no attempt to segregate waste typesaccording to their chemical content or the relative stability of the waste packages. In general.little compaction was applied to the disposed waste. bac,kfill, and trench covers other thanthat obtained by driving over the disposal trenches with heavy trucks. Thus. considerablevoid space probably existed within the trenches, promoting rapid settling. At the humid sites.water from rainfall was frequently allowed to accumulate in the open disposal trenches whilethey were being filled, promoting rapid waste degradation and settling. In many cases, thesoil surrounding the trenches was iesspermeable to water than the soil that was used to coverthe trench. This difference in permeability allowed the trenches to fill with water, aphenomenon known as the “bathtub” effect (INEL. 1994).

The characteristics of several of the disposal site locations also contributed to theproblems. Low-permeability soils retained the water that entered the disposal units. allowing, .it to become contaminated with radionuclides before its slow release. Sand lenses served toroute groundwater into and out of disposal trenches. At Sheffield. a permeable layer at thebottom of the trenches conducted contaminated water away from the trenches and off-site.At Maxey Flats, a permeable layer provided communication between trenches. At WestValley, the low-permeability material surrounding the trenches caused infiltrating water to

fill a trench and seep out through the cover system.

Problems of this magnitude and typ,e were not experienced at Richland, .Bamwell.’ andBeatty. The Richland. Washington, site and the Beatty, Nevada. site are in arid to semi-aridenvironments and do not experience water management problems. The site at Barnwell,South Carolim, although in a humid environment. has benefited from the experiences of theother sites.

The experiences in the developmental years of commercial LLW disposal led to theformulation of 10 CFR Part 6 I by NRC in 1982. The goal of this regulation was to attainfour performance objectives:

. protect the general population from releases of radioactivity.

. protect any individual who inadvertently enters a disposal site after the site is closed.

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. protect workers during site operations. and● ensure long-term stability at disposal sues to ehminate the need for ongoing active

maintenance after closure.

The DOE formalized its Order 5820.2A for LLW disposal in 1988. The goal of the Order is ,to also attain four performance objectives:

. protect the public health and safety in accordance” with applicable standards.

. protect the general population from releases of radioactivity,

. protect an individual who inadvertently enter a disposal site after the site is closed. and

. protect groundwater resources.

Both NRC and DOE require performance assessments to be done. and theperformance standards for permissible doses are similar. NRC requires that the sitecharacteristics be considered in terms of the mdeftnite future and evaluated for a 500-yeartime frame. The DOE requires that the potential for natural hazards such as floods. erosion.tornadoes. earthquakes. and volcanoes be considered in site selection. The site selectlonshould also address the impact on current and projected populations. land use resources anddevelopment plans. The NRC and DOE both require consideration of long-term site

characteristics and mechanisms for contaminant release.

Although there are differences in implementation. the approach used by NRC andDOE for many aspects of LLW disposal are similar. This similarity should not be surprising:the NRC and DOE evolved from the same parent organization, the Atomic Energy

Commission, and the NRC and DOE have continued close interactions related to disposal ofLLW. For example, the NRC relied on the DOE national laboratories to help provide thetechnical basis for its LLW rule. The effects of the differences in approaches used by theNRC and DOE are identified m this report.

Purpose

This report results from the Secretary of Energy’s response to DNFSBRecommendation 94-2. Specifically. it .ierves as the basis for establishing the guidelines setfor Task 4: J7valuation of Privati7 “w of Chapter IV of the Implementation Plan forRecommendation 94-2 (DOE, 1996b). The purpose of this deliverable is to compare thesafety merits and demerits of using prtvately operated facilities (i.e., tho~e not part of theLLW compact system) for the disposal of DOE LL W relative to using DOE manageddisposal facilities. The evaluation is based on seven functional areas: siting, design,operations, closure, waste form, performance assessment, and approval and oversight.

A report that compares and outlines the major differences in the approaches used byNRC and DOE to regulate and manage disposal of LLW for these same seven functionalareas has recentiy been prepared for DOE (Cole et al., 1995). While the comparisons of

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approaches contained in that report serve as a data source for this work. the usefulness of thatreport 1s limned because it contained no analyses and little discussion pertaining to thebenetlt of one approach over the other. Those types of analyses and discussions arecontained in this report.

Approach. .

For each of the sevenand managmg LLW disposal

functional areas. the DOE and NRC approaches to regulatingare compared and the safety merits and demerits of using

pr~vate tacilines are identified. To the extent possible. the differences in these twoapproaches are qualified and quantified. ”The ,quarmtative differences in the approaches arederived by comparm~ site-specific commercial waste acceptance criteria ~vlth resultscompiled from various DOE reports about the performance of specific and generic disp&alfacilities. A systems approach is used to identi@ the differences in privately operated andDOE-managed disposal facilities using the seven functional areas. Differences in sitecharacteristics (e.g., hydrology) are included as part of this systematic evaluation.

.The next section of the report provides a comparison and dis&ssion of the seven

functional areas and highlights the differences between privately operated and DOE operatedchsposal facilities. The last section of the report contains conclusions based on theseanalyses.

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COMPARISONS BY FUNCTIONAL ARE.4S

This section provides comparisons of privately operated and DOE-managed disposalfacilities based on seven fictional areas: siting. design. operations. closure. ~~’asteform.performance assessment. and approval and oversight.

Siting

For privately operated LLW disposal facilities licensed by the Nuclear Regulato~Commission or an Agreement State. the selected location must meet the siting requirementslaid out in 10 CFR Part 61. The purpose of the siung criteria is to select a location lvhich is .satisfacto~ for a disposal facility that will contain Class A, B. and C wastes. The Part 61 “smng criteria include requirements for:

● cnoosmg a location tvhich can be chamcterlzed. modeled. analyzed. and nmn]twui.● avoiding Iocatlons of population growth. future development. or where nearb~ facilities

could adversely impact the site.● avoiding locations that {1) have known natural resources, (2) are in flood plains. (3) have

a significant upstream drainage area. (4) are known active tectonic or volcanic areas. (5)have surface geologlc processes occur often. and (6) the ground water discharges to thesurface within the disposal site. and

.0 choosing a location with sufficient depth to ground water. or with ground water in whichmolecular diflision is the dominant means of transport.

The typical approach for meeting these criteria has been to apply a screening processwith pre-established criteria to all the land within a state’s boundary and to eliminate fromconsideration areas of the state that faii the screening criteria. The areas that remain after thisscreening are considered potential sites for fhrther evaluation. Concerns have been identifiedabout this type of screening process based on the lack of success to date, on shortcomings inthe amount and quality of technical data available for screening, and on professionaldifferences abou~ the. importance of various screening requirements (’Newberry. 1994).

For DOE facilities that dispose of LLUT. the siting requirements are contained in DOEOrder 5820.2A (DOE, 1988). While the requirements of NRC and DOE are similar (seeTable B- I in Cole et al.. 1995), one major difference is apparent. ‘The DOE is limited toselecting locations from within the boundaries of the reservations under its control. Ingeneral. the locations for these reservations were selected for reasons other than for theirsuitability for disposal of LL W. although. in general, suitable locations for disposal havebeen found at these sites.

Both the DOE and NRC use a defense-in-depth approach for systematic design ofdisposal facilities. This defense-in-depth approach includes performance of the surroundingenvironment. design of the disposal facility, selection of waste form. ahd limits oninventories of radiologically significant radionuclides. The following examples are derivedfrom performance assessments for disposal facilities for DOE LLW. although in principle.

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the concep~s apply to both DOE and privatel~- operated facilities. More detail on thequanntauve aspects of the disposal facdit}’ design and waste form are provided in latersections of the report.

The geologc and hydrogeologlc characteristics of the environment surrounding someDOE disposal facilities are relatively complex. For example. at Los Alamos NationalLaboratory (LANL). the vadose (unsaturated) zone m thearea of the LLV’ disposal facilit!consists of approximately 750 feet of welded and rmnwelded ~’olcanic tuff w’lth purnlcemterbeds that overhe approxlmatel~’ W(3 feet of conglomerates Ivith basalt lnterbeds. .Ai theIdaho Nauonal Engmeermg Laboratory (I’NEL ). the vadose zon~ m the area of the LLM’”disposal facility consists of a series of basalt flows with silty interbeds of sedimentarydeposits extending to great depths. The basalt ilows are strongly fractured and fissured andexhibit a classic structure of massive rock in the center grading to highly vesicular rubble a[the top and bottom. At the Oak Ridge Reservation (ORR), the vadose zone is thin ‘ornonexistent. and the water table is a subdued replica of the surface topography that 1sconstrained by ground surface elevations at streams. Groundwater normally discharges tostreams. Additionally, the groundwater flows in fractures and weathered zones that are

generally parallel to geologic strike. causing severely anisotropic flows (DOE. 1996a).

The complex geology at LANL. INEL. and ORR were modeled in the performanceassessments for those sites in a simple and conservative manner. At LANL. the welded tuffscontaining or suspected of containing fractures were not included in the analysis ofperformance. and the effective thickness of the vadose zone was reduced by approximately50 meters (DOE. 1996a). At INEL. the basalt flows were not included in the analysis ofperformance, and the effective vadose zone thickness was reduced by approximately 220meters (iMaheras et al.. 1994). At ORR. [he tumulus disposal facility was modeled as if a“bathtub effect” would result. and compliance points were established at surface waterlocations predicted to receive the contaminated groundwater and at groundwater locations.even though these groundwater formations could not sustain water production rates requiredto support a drinking-water well. The groundwater compliance point was shown to providethe most restrictive limits for releases from the disposal facility (ORNL, 1994).

The actual degree of conservatism that results from the simplifications of thesubsurface geology provided in the performance assessments for these three sites cannot beestimated (see. e.g., Oreskes et al.. 1994). However, the simplifications used in theperformance assessments lead to defense-m-depth by foregoing credit for the zones ofcomplex geology that likely provide some attenuation.

In the arid or semi-arid region of the count~ at Hanford, INEL, LANL. NTS, and

Envirocare, facilities for disposal of DOE LLW are shallow subsurface trenches. In thehumid region of the country at ORR. SRS. and Bamwell, however, tumulus and vault

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technologies are used for disposal facdlties. The prtmary benefit of these more-engineeredfacilities is hydraulic isolation of the was~es because the large amounts of low-permeabilit}concrete used in these facilities effec~ively isolate the wastes from infiltrating water.

The absolute service life of the tumulus and vault facilities is not kno~vn due to thelack of long-term experience with these facilities. The performance assessments at ORRIORNL. 1994) and SRS (MMES et al.. 1994) address this uncertain> b} makingconservative assumptions about the duration of performance for these facilities based on theirstructural stability. The engineered barmers in these facilities are assumed to fail at somepoint in the future. and the facility is then assumed to perform no better than the surrounding.environment. The primary consequence of this assumption is that engineered faci Iities areassumed to offer no sxgriificant long-term advantages for the disposal of wastes containinglonger-lived radionuclides. The prima~ advantage of engineered barriers is for the disposalof wastes containing shorter-lived radionuclides. This discussion also applies to the Barn\vel!commercial LLW disposal facillty near SRS. ivnlch recentl> started using \ault faclllues.

Waste FomI

The primary purpose of using specific waste forms for disposal of LLV: is to providestructural stability for the disposal facihty Failures of early commercial disposal facilities atMaxey Flats. Sheffield, and West Valley were prlmaril y the result of the interaction of waterwith the waste from subsidence cracking of the cover systems due to consolidation of

unstabilized waste.

Another purpose of using specific waste forms 1s to minimize mobilization ofradionuclides. The performance assessments for the LLW disposal facilities at ORR andSRS use conservative estimates for the release of radionuclides from wastes relative to theexperimental evidence. both in terms of magmtude of release and delay prior to release. Inboth performance assessments, grouted wastes are modeled by diffislon and desorptlonprocesses. The desorptlon processes are conservatively modeled by selecting lower valuesfordesorption parameters (i.e.. K~ values) than are believed to be measured in the stabilizedwaste. This approach results in assumed calculated releases of radionuclides that are higherthan are expected to occur under disposal facility conditions. As with more-engineereddisposal facilities, shorter-lived radionuclides tend to benefit most fromforms because they decay to low levels while entrapped in the waste.

enhanced waste

4im ting]nventorie~

Limits on inventories for the radionuclides in LLW are determined from site-specificperformance assessments for both DOE and privately operated facilities. These site-specificperformance assessments incorporate the performance aspects of the specific geologic and .hydrologic conditions of the site when estimating permissible limits on radionuclides. Otheranalyses, such as facility safety analyses, are also used to provide limits on inventories ofcertain radionuclides. Privately operated facilities are prohibited from accepting waste that 1sgreater-than-class C. The DOE Order requires that wastes that are equivalent to greater-than-

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class C. as defined in 10 CFR Part 61.55. must be handled as special case waste and are

generally not suitable for disposal in near-surface LLW disposal facilities. Because of thesimplifications and conservatism used in the performance assessments for disposal facilitiesfor LLW. the estimates of limiting concentrations of radionuclides are lo~ver than those thatwould be provided by a more realistic analysis of performance. These lower limits are thedeliberate result of an approach that attempts to use conservatism to counteract theuncertamt~ associated with complex hydro]oglc enwronments and engineered dlsposaifacdities. . .

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Summary C_ison of DOF, and Prl\’alel\ O~erated Facilities - Siting

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Developers of privately operated disposal facilities are required to follow strictguidehnes for siting these facilities. TINSrequirement has generally resulted In a slte-screening process based on exclusionary criteria that is often challenged on the basis of lackof data and disagreement about the importance of the selected technical t’actors. Site-speci Iicperformance assessments are used to de~ermine permissible concentrations of radionuclides.which are incorporated into the WAC based on the license granted by the NRC or AgreementState. Wastes with concentrations of radionuclides determined to be greater-than-class C areprohibited from disposal at privately operated facilities.

The DOE selects sites for its disposal facilities from within the boundaries of itsreservations and determines the perrmssible inventories of radionuclides for disposal basedon performance assessments and other safety documentation. The DOE also generallyexcludes wastes that are designated as greater-than-class-C. as defined in 10 CFR Part 61.55.from disposal in near-surface LL W facilities (DOE. 1988). Similar to pnva[ely operatedfacilities. this exclusion effectively places an upper limit on the concentrations of certain “radionuclides in waste disposed of in DOE LLW facilities.

It may be expected.that siting for privately operated facilities would result in

geologically more suitable locations than those chosen by DOE because the process for theprivate facilities generally begins with a much larger universe of potential disposal locations.However, as discussed ill later sections of this report. this may not always. be true. First., the

regulatory thresholds for radionuclide concentrations in commercial and DOE LLW (i.e..Class C waste limits) effectively result m a search for sites that are sufficiently adequate tocontain these wastes. When site-specific characteristics or other reasons dictate, additionallimlts on concentrations of radionuclides are placed on the waste accepted at both DOE andprivately operated facilities. Second, some DOE reservations are located in areas that areextremely amenable to disposal of LLW (see the discussion of NTS in the PerformanceAssessment section of this report). Therefore, although the NRC and DOE requirements andpractices for siting disposal facilities are different. no clear safety merits or demerits of usingprivately operated facilities are evident based on siting considerations.

s

Design

The type of design selected for the disposal facility 1s a ke~’ factor in limitlnginventories of radionuclides that can be disposed of at a particular site for both releases to

the environment and inadvertent intrusion. In the assessment of performance of disposalfacilities for LLW: the selected scenanos for inadvertent intrusion are usual l}”sho~~~ to Iiml[the permissible inventories of many radionuclides at most sites. However. for severalradionuclides. releases from the disposal facility to the environment are important forlimiting inventories, especially at sites in humid regions of the counr~ (e.g.. ORNL. 1994:MMES et a!.. 1994).

The type of disposal facility designs used at both current]]- active DOE sites and .prlvatel} operated disposal sites are listed in Table 1. At sites in humid regions of thecount~. ~e.g.. ORR, SRS. and Barnwell). facilities u’ith additional engineered features areused.

Table” 1. Facility Designs Used at LLW Disposal Sites (from Cole et al.. 1996a).

~ State Disposal FacilityDesign

,DOE Hanford Reservation Washington Trench Vault

DOE Idaho National Engmeenng Laboratory (INEL) Idaho TrenchDOE Nevada Test Site (NTS) Nevada Trench

DOE Los Alamos National Laboratory (IANL) New Mexico TrenchDOE Oak Ridge Reservation (ORR) Tennessee Above-grade Tumulus

DOE Savannah River Site (SRS) South Carolina Above-grade VaultEnvirocare Utah Trench

Barnwell South Carohna Below-grade Vault

In this section, the differences in performance of trench, tumulus, and vault disposalfacilities are identified. Performance is measured in terms of limiting concentrations ofradionuclides m waste with respect to releases to the environment. To make thesecomparisons. the results of the performance evaluation (PE) project (DOE. 1996a) are used.That pro!ec~ evaluated several different sites for disposal of mixed low-level waste (MLLW’)using genenc trench and tumulus facilities: a vault facility was evaluated at SRS because thatsite was using vault technology. Although developed for evaluating options for disposal ofMLLW7. the PE is applicable to LLW disposal because the performance of MLL W disposalfacilities ~~ereassumed to be similar to those for LLW. Site-specific performanceassessments were not used in the analysis of design because they evaluate only the disposalfacilit}’ design plamed for that site and therefore, do not provide results relative to differentdesigns.

To facilitate the discussion of environmental behavior. the 58 radionuclides evaluatedm the PE project were grouped into 8 categories according to persistence (i.e.. half-life).mobility. and radiotoxici~y. An indicator radionuclide was chosen to represent each of the 8

9

*

categories (Table 2). While all 58 radionuclides

..

cannot be definitively categorized into asingle one of the eight groupings. a generalized grouping is shown in Table S. AS aconsequence of the impact of radiologically significant decay products. some of theradionuclides appear m more than one grouping. Because transport values of radionuclidesdepend on localized conditions. site-specific groupings maybe different than those presentedhere

Table 2. Characteristics of the Indicator Radionuclides (’from DOE. 1996aj.

Radionuclide Half-Life (years)

H-3 Short 12.3 Phgh and Volatde Low

C-14 Medium 5700 High and Volatile ! Low

- Sr-90 Short 29.1 High Medium

Tc-99 Long 213.000 I Hign Low

Cs-137 Short 30.2 Medium Medmm

U:238 I Long 447 billion Medium Medium

Pu-239 Long 24,100 Low High

Am-241 Medium 433 Low High

(NP-237)’(Long) (2.14 million)

~ (High) AHalf-life - Shott: t,ns 30y; Medmm: 30< t,n s 10.000 y: Long t,n>10.000yMobihty - Htgh: Kds 5 mUg: Medium, 5< K. s 100 mUg: Low: K.> 100 mUgRadlotoxlclty - Low. PDCF s 1 (rem/y )/(mCi/L): Medr.im. 1< PDCF s 100 (rem/y )/(mCi/L); High: PDCF >100 (rem/y )/(mCi/L,a Although No-237 IS a decay oroduct of Am-241 it nas slgmficantly different properties See text for dlscuss!on of this mdlcator

radlonuckle.

1

10

..+

Table 3. .4 General Grouping of the 58 Radionuclides Evaluated in the PE (from DOE.1996a’). .

Indicator Nuclides with Similar Half-Life and Mobility CharacteristicsRadionuclide

H-3 Volatile

C-14 Volatile

sr-90 CO-60, Cd-1 13m, Ba-133

Tc-99 (I-129)’, (Np-237), (Am-241)b, (Pu-241 )’

CS-137 (Nb-93mJ. Eu-152. Eu-154, (Pb.210), (Ra-228)

U-238 (Al-26 ).( Cl-36 ).( KAO), (Pal-l 07), U-233 .U-234, U-235, iU-236), Pu-238c" “.”

PU-239 (Ni-59), !Se-79) (Zr-93). (Nb-94j (%-126), (CS-135). Th-230 Th-232, Pa-23: ,Pu-242, Pu-24A Cm-24& Cm-247 Cm-248 I

Arn-241e [SI-32). (NI-63). ~Ag-105im) (S~-121m J, (Sm-151). Ra-226. Th-229 U-2321’

Pu-238. Pu-240, Pu-241’, Am-243, Cm-244G, Cm-245, Cm-246. Cf-249, Cf-250r ‘cf-251

Parentheses indicate that toxlclty category IS different than for !nd[cator rachonucllde,Am-241 and Pu-241 are CIased on theu decay mocluct Np-237The charactertstlca of Pu-238 are Oased on Its aecav product U-234The cnaractenstics of Cm-243 are based on Its decay oroctuct Pu-239The listed radlonuclides are slmtlar to Am-241 only for early arrwal times at the performance boundary Because theseradlonucl!des have medium rialf-hves and are generally of low moblhty, later arrival t!mes WIII result m slgruficant radloactweaecay Later arrival I!mek for Am-241 result m its mobile. Iong-lwed, radiologically significant decay product. NP-237.contributing significantly to the aase.The cnaracterlstica of Pu-241 are based on Its decay oroduct Am-241,The charactenstm of Cm-244 are based on Its aecay oroduct Pu-240The characteristics of Cf-250 are based on Its aecav proauct Cm-246.

Perfoumnce of Faciliw D- for the Water Pat hway

The permissible concentrations of radionuclides in waste for each of the indicatorradionuclides based on the analysis of the water pathway for the 6 DOE LLW disposal sitesare shown in Figure 1. for both the ~rench and mmulus designs. Results for the vault design atSRS “are also. included- These sites represent a wide range of climates and site conditions.

For shorter-lived, mobile radionuclides represented by tritium (H-J), the vault facilityat SRS and the tumulus facilities at all sites, except NTS and LANL, allow increasedpermissible concentrations that are several orders of magnitude greater than those for thetrench facility. This increase is primarily due to the assumption that the tumulus and vaultfacilities minimize infiltration of water for much longer periods than the trench facility; thus.the shorter-lived radionuclides decay while still within the tumulus or vault facility. Thepermissible concentrations of these radionuclides in waste at NTS and LANL are unlimitedfor the water pathway. At NTS, an assumption used in the PE and performance assessment(Shott et al., 1996) is that there is no downward migration of water to the regional aquifer.At LANL, the long water travel time in the vadose zone causes tritium to decay to very lowlevels in the vadose zone.

11

The differences in permissible concentrations between the trench and tumulusfacilities for medium- to longer-lived radionuclides of medium to high mobil it} (e.g.. C- 1-1.Tc-99. and L.~-238) are minor. The assumed differences in duration of these facility designsare small relative to the half-lives of these radionuclides: the only effect is that theradionuclides are detained in the facility until the engineered barriers are assumed to fail. Forthe vault design at SRS. the perrmssible conceniratlons for C- 14 are approxlmatel} 2 ordersof maqmude hqgher than those for the trench and mmuius designs due to the longer detentionassumed for the vault (3000 years) (MMES et al.. 1994) relative to the trench t 100 years ~andtumultii (300 years) facilities and relative to the half-life of C- 14.

For the shorter-lived radionuclides of medium to, low mobility that are represented b>Sr-9@and Cs-1 37. the permissible concentrations are unlimited for most sites for both thetrench and tumulus facilities. These radionuclides decay to low levels while migratingthrough the enwronment prior to reaching the performance boundary. For longer-llvedradionuclides like Pu-239 and Am-241 (and its radiologically significant decay productNp-237). differences in permissible concentrations between the trench. tumulus. and vaultfacilities are minor.

Because of the increased amounts of iniiltratmg water. the permissible concentrationsbased on the water pathway for sites located in humid regions of the countq (e.g.. ORR.SRS. and by extension, Barnwell) are generally lower than for”the sites located in aridregions of the country. The increased amount of infiltrating water is a primary reason thathumid-zone sites use more engineered tumulus or vault disposal facilities. The principalpurpose of these engineered facilities IS to prowde hydraulic isolation of the wastes for longerperiods of time. a requirement not as Important at sites located in the arid region of thecountry

. . H-3 I1E+16 y—-=- <~o Lmwt I1E*14 ~

I - k

IE+12 ;

‘E 1E+1o ; .——

~ lE+os jorre?lOl● runulul

=1 E+06 ? o vault

IE+04 ; I

1E+02 ;IE+OO =

I ● ☛

U-238 ‘lE+16p1E+14 ~

1E+12 ;

“E1E+1O i

~ 1E+06 ;= 1E+06 ;

1E+04 ~

lR-1E+02 ~1E+OO

g

;

___ No bm!t

———0 trmm● wnuluso vault—

● ., ——

ma‘*-II -

1E+14 ;

IE+12 ~ II

“$ lE+oE;~ 1E*06 +

h_.ll_&

OVWR1E+04 ~

m

n1E+02 ;lE+oo - —d.1

1

f . . . . . ..“ Sr-90 ““

IE+l

1

1E+14 “?

1E+12 ~

‘EIE+IO ?

~ 1E+08 -r

al E+06 -*.r

1E+04 ~

1E+02 ~1E+OO -

Pu-239 “

F

No LMt

—O trench

● lumutus

Ovaun—.

—, ——-d...

~No Limit

mlo

*,

,

*

!i5RG-I:otumuu.u,,1Ovaull

.-Am-241

1E+16 ~lE+ld ;

1E+12 ;

‘E 1E+1o ;

~ 1E+08 ;

= 1E+06 :1E+04 ;

n1E+02 ;lE+oo :

~. Limit

.; Otrunnmmutu5.

1E+16 ~1E+14 ‘

T1E+12 ~

“E1E+1O ?

= 1E+08 ~, c% 1E+06 ~

M

1E+04 ;

1E+02 ;1E+OO ; _

~o Umit

....~ o tralun8 tumutuso vault——.

flflbl ““-● Arrival ttme greater than 10,000 y

● Cs-1 37, U-238, and Pu-239 were not evaluated in the SRS PA water pathway analysis

Figure 1. Permissible waste concentrations (mCi/m3) for the water pathway (from DOE. 1996a).

13

..#

. .of F~o v“ n vs. the Water Pat hw~

The scenarios toevaluatethechronic,long-term exposures to an inadvertent intruderat DOE sites in humid environments (e.g., ORNL, 1994 and MMES et al., 1994) include ahomesteader scenario and a “post-drilling” scenario. In the homesteader scenario, the.homesteader’s house is constructed above the disposal facility with the basementextending.into the partially exhumed waste. A portion of the exhumed waste is placed in the soil of thefahily’s garden piot. Exposures occur through external exposure while in the house and

garden and through internal exposure from ingestion of contaminated foodstuffs andassociated soils. This scenario was assumed to occur afie~ 300 years for the trench facilityand atler 500 years for the tumulus facility.

In the post-drilling scenario, the homesteader’s water well is drilled through the _-disposal facility, and the cuttings are mixed with the soil of the family’s garden plot.Exposures occur though external exposure while in the garden and through internal exposurefrom ingestion of contaminated foodstuffs and associated soils. This scenario was assumed tooccur afier 100 years for both the trench and tumulus facilities unless site-specific conditionsdictated otherwise. While the post-drilling scenario provides for less interaction of intruderswith waste, the earlier assumed time of intrusion causes shorter-lived radionuclides to belimited by this scenario. The limiting concentrations in waste for the indicator radionuclidesbased on the intrusion scenarios are shown in Figure 2.

f

I TrsnchlE*lz

1E*1o

‘~ 1Eu3!3

~ lEKM.—. —.-_—‘Oliomesteaoer

100W ■ Pos[-amhng-— ______ _100

1?:x“ 8~~8z:

h:. ~

~$Indkator Ra;ionuclldo

I Tumulus

nr--------------. No Llfit

1E*12 I# I

“E 1E+08 —..—. . .E=l E-IX oNOmesleaOOr

l@xomPOst.orlulng

100

*7 zq;~~fizxv

lz:.~=;

Indicator Ra;onuclid~

Figure 2. Permissible waste concentrations (pCi/m3) for the trench and tumulus designs

for the standard intrusion scenarios (DOE. 1996a).

14

.

‘*

●

A comparison of the limiting concentrations in waste for the indicator radionuclldesbased on the water pathway and on the scenarios for inadvertent intrusion indicates thefollowing:

For sites in arid. and semi-arid regions (e.g.. NTS. LANL. INEL. Hanford. and b}extension. Envirocare ). the water pathway will limit concentrations for onl}- the longer-lived and highly mobile radionuciides like Tc-95 regardless of the type of disposalfacdity used. Therefore. the trench facilities. which’ are less cmtly to develop andoperate. are typically used at these sites.

For sites in the humid region of the count~ (e.g.. ORR. SRS. and b} extension..,

Bamwell), the water pathway is more important for limiting radionuclide concentrations.The more-engineered tumuius and vault facili~ies will permit higher llmits of shorter-lived radionuclides thaq will the trench facilities. However, because the differences masstimed time of perfommnce between the tumulus. vault. and trench facilities are smallrelative to the half-lives of longer-lived radionuclides. there is little difference inperformance of any of these facilities for the longer-lived radionuclides. Tumulus andvault facilities are now typically used at these humid sites.

The permissible concentrations and inventories for the shorter-lived, mobileradionuclides will increase most from the use of more engineered facilities. The permissibleconcentrations for the longer-lived radionuclides do not increase appreciably from use ofmore engineered facilities because the engineered features are assumed to perform for a finiteperiod of time. Beyond this time. the longer-lived radionuclides. which have decayed byon]y a m]nor amount, can migrate from the disposal facility and t]lrough t]le ell~llromellt atrates dependent ort site conditions rather than on facility conditions. Therefore. the primaryadvantage of engineered barriers in tumulus and vault disposal facilities is fordisposal of

wastes containing shorter-lived radionuclides. Engineered barriers offer no significant long-term advantages for the disposal of wastes containing longer-lived radionuclides.

The sites that benefit from use of more engineered facilities are ORR, SRS, andBamwell in humid regions of the country, and these sites already use additional engineeredfeatures. For disposal sites in arid and semi-arid regions of the country (i.e.. NTS. INEL,Hanford. LANL. and Envirocare), the differences in performance between trench. tumulus.and vault facilities are minor, and these sites have typically used the lower-cost trenchfacilities. Therefore, based on design considerations, there is no apparent safety merits ordemerits for using privately-operated facilities for disposal of DOE LL W.

#

Operations

In this secuon. the activity tracking systems used by DOE at their LLV’ disposalfacilities are discussed. Also discussed are the safer aspects of using a uas~e classlficauonsystem, The safety merits and demerits of using privately operated disposal facilities forDOE LLW are summarized. The comparison of the operauonal safet] and health of \vorkersat DOE and privately operated facilities is beyond the scope of this report. and metrics suchas accident rates and worker exposure were not examined. However. it should be noted thmboth DOE and privately operated facilities must mee~ requirements (e.g.. OSHA. NRC, orDOE Orders ) that in general are similar.

For privately operated facilities. the NRC has established a waste classificationsystem ~vith three categories of waste that are acceptable for disposal in a near-surface burialfacility. Using this system. wastes hawng greater radiological hazards are required to bedisposed of with greater protection. The waste classification system in 10 CFR Part61consists of three classes: Class A. Class B. and Class C. Class A wastes contain lowerconcentrations of shot-ter-llved radionuclides. These wastes can be disposed of w[th only theminimum waste form requirements. Class B and C wastes contain longer-lived radionuclidesor higher concentrations of short-lived radionuclides and require additional packaging andmore isolation. The WACS for privately operated facilities are based on the license grantedby NRC or the agreement state and maybe different than the limits based on the NRCclassification system. For example. the license for Envirocare places limits on concentrationsof radionuclides that are similar to Class A waste.

The DOE installations that operate disposal facilities are required by DOE Order5820.2.4 to develop and implement facility operating procedures that protect the environmentand the health and safety of the public and facility personnel; ensure the security of thefacility: minimize the need for long-term control; and meet the requirements of theclosurelpost closure plan. Operating procedures include training for facility persomel.emergency response plans, and a system of reporting unusual occurrences.

Disposal of DOE’s LLW is to be achieved by methods appropriate for meeting the

performance objectives. For each disposal site, engineered modifications (e.g., stabilization.packaging, burial depth, and barriers) to handle specific waste types and compositions mustbe evaluated as part of the performance assessment process. In the course of this process,site-specific waste classification limits may be developed to determine how specific wastesshould be stabilized and packaged for disposal. The Order also specifies requirementsintended to improve disposal site stability and facilitate waste handling, including specifyinglimitations on waste characteristics and packaging designs. The DOE has chosen to rely onthe performance assessment results to determine the \vaste acceptance criteria of the disposalfacility rather than having predetermined low-level waste classifications.

16

#

Act ivim Trac~

The radiological WAC for a disposal facility for DOE LL W are based on theperformance assessment and safety analysis reports (SAR) fort hat facility. The performanceassessment provides information that results in limits on inventories or concentrations ofcertain raciionuclides based on estimates of long-term performance of the facility The”SARprowdes similar information based on analyses of operations of the facility and impacts tothe public and site operations personnel,

The Iimlts on mventones or concentrat~ons generally appl> to the total facillt!. - “Except \\”here noted m the SAR. these analyses provide no direct correlation for limlts onmdividuai packages of waste. Instead of applying concentration limits based on the facilit}scale to individual waste packages. the DOE facilities disposing of LL W’have de~’elopedinvento~ tracking systems (i.e., record keeping systems) to ensure that the total inventoriesof important radionuclides are kept below the inventory limits established by the perfopnanceassessment for the entire facility.

In implementing these tracking systems. special consideration is given to high acti~itywaste packages or the radionuclide inventories exceeding a substantial fraction of the facility“limits (e.g.. 10?40or more). The types of considerations that are used in these cases includeboth requirements for advanced warning and/or special approvals before shipping fordisposal, and provisions in the design of the disposal facility to ensure that such unusualwastes ~vould be relatively “inaccessible after disposal. The degree of concentration averagingprovided by this approach must be consistent with the exposure and release scenarios used to

develop the inventory limits for the disposal facility. These guidelines were intended toreflect a common sense approach to ensuring acceptable disposals and to prevent abuses ofreasonable methods of concentration averaging (Wood et al., 1994).

The DOE approach for these unusual wastes is similar to that used by NRC for ClassC wastes. in that DOE’s requirement to make the wastes “relatively inaccessible” ii similar toNRC’s requirement to place Class C wastes at least 5 m below ground surface and to placeintrusion barriers over them. The DOE approach provides for more flexibility for disposal ofwaste but requires more frequent and close interaction between the waste generators and

those operating the disposal facilities.

Waste Classification Svstem

The NRC regulations for privately operated disposal facilities include the use of awaste classification system. One of the factors used by NRC in developing a wasteclassificauon system was that disposal facility operators must accept waste as delivered tothem (NRC. 1982, p. 5-2’3). The NRC staff stated that a waste classification system, which

would set requirements that must be met by waste -generators. \vould be the most reasonableway of ach]eving the performance obl ectives and tec’hmcai criteria for disposal facilities.

The approach of NRC for developing a waste acceptance criteria that minimizesinteraction between waste generators and waste disposers was practical for their particularsltua~ion because without such a system. the large and varying number of ~vaste generatorswould make the necessary interactions with waste disposers extremely difficult. Because the

operarors of disposal facilities for DOE LL V’ have a smaller number of waste genei-ators withwhich m deal and because the wastes generated by DOE can vary greatly in form and ‘”radionuclide content. a waste classification system similar to that of NRC has never been” ,’adopted by DOE.

Summw comparisonof DOF andr PrivateI\’ O~erated Fa cilities - Ope rations

Operationof private disposal facilities utilizes waste segregation based on the wasteclassification system developed by NRC. This system pro~’ides an effective interfacebetween waste generators and waste disposers that minimizes the need for their interaction.Privately operated sites consider this classification system when developing their WACS,which are based on site-specific performance assessments and result from licenses granted by

the NRC or Agreement States.

DOE bases its operational WAC on the results of site-specific performanceassessments and SARS. The radiological limits vw from site to site based on the capabilityof the natural and man-made features incorporated into the design. An activity trackingsystem 1s used to ensure that the total inventory of each important radionuclide is maintainedbelow the facility limits. The application of this tracking system for wastes with higheractivities of certain radionuclides is similar In approach to NRC’s treatment of Class C waste:it provides for additional isolation of these wastes. While the activity tracking systemapproach provides more operational flexibility for DOE. It does not appear to result in anysafety merits or demerits relative to using an NRC-style waste classification system.

Prior to their acceptance, DOE LLW that are being considered for disposal inprivately operated facilities must be qualified based on the WAC for that disposal site.Therefore. there appear to be no significant safety merits or demerits of using privately

operated disposal facilities for DOE LLW based on operational concerns.

18

.8

Closure9

Closure of a disposal facility comprises a set of systematic actions after wasteemplacement operations are completed. Closure includes alI the necessary actions to put thefaciiity in the required configuration m enter the post-closure period. to achieve radiationprotection goals. and to fulfill envuonmental reqmrements. The components of closure are .

●

●

●

●

●

●

Completion of disposal facilit!- operations and installation of tlie’cover system.

Dwnantling of auxiliar} ticilitles and engineered systems.

Collecnon and management of records.

Preparation of a post-operation safety report,

Finalization of an environmental survey program, and

Obtaining regulatory approval of the closure plan and institutional control provisions.

A comparison of the regulatory guidelines for privately operated facilities and DOEdisposal facilities has been detailed in Cole et al. (1995) and is summarized here. Theregulations in 10 CFR Part 61 govern privately operated facilities for LL W disposal. Adescription of the plans for site closure and other long-term issues must be addressed by thelicensee in the license application (Section 61,12). These plans. although preliminary, areused in the development of the performance assessment for the facility.

AS a method to ensure long-term institutional control, privately operated facilitiesmust be located on lands leased from s[ate or federal government entities. In Section 61.29,the licensee is required to obseme, monitor, and c&-ry out all necessary mainten~ce andrepairs at the disposal site before the license is transferred by the Commission.Responsibility for the site must be maintained by the licensee for 5 years after closure and,based on site-specific conditions a shorter or longer time period for post-closure observationand maintenance may be established and approved as part of the site closure plan.

When the requirements for closure are met, control of the waste and surrounding landreturns to the control of the government entity. The NRC requires a surety bond that willprovide fimds for environmental restoration in the event of disposal facility failure (Section “

61.63). Section 151 of the Nuclear Waste Policy Act of 1982 gives the Secretary of Energythe authority to assume title and custody of inactive disposal facilities if requested and if thefacilities mee~ all closure requirements of the NRC.

19

..*

For the DOE-managed facilities. the DOE is committed to retaining control ofcontaminated lands until they can be released under provisions contained in DOE Order5400.5 {expected to be codified into 10 CFR Part 834). The primary requirement of thisOrder is to ensure that the measured dose to a member of the public from all sources ofexposure is kept below 100 mrem per year. The DOE is currently evacuating potential futureexposures from combined source terms near LL W disposal facilities using compositeanalyses axialwill evaluate the impact of all combmed sources on their resemauons using‘-comprehensive analyses”’ (D.OE. 1996bj. . .

DOE Order 5820.2A, Section 3j( 1) (DOE. 1988) states, ..Field organizations shalldevelop site-specific comprehensive closure plans for new’and existing operating LLW ~disposal sites. The plans shall address closure of disposal sites “within a f-year period at?ereach disposal site is filled.” However. as identified in vulnerability number 6 of DOE’s‘.Conlpiex-Wide Review (C WR) of DOE’s LLW Management ES & H Vulnerabilities.”(DOE. 1996c) for Recommendation 94-2. closure plans for some sites have not beenprepared. and assumptions about the configuration of the closed facilities are being made inthe performance assessments, This issue is being addressed by the corrective action plandeveloped to resolve the vulnerabilitles identified in the CWR.

The Order provision to analyze site performance for a worst case scenario of the lossof institutional control after 100 years has been widely misinterpreted. The promulgation of10 CFR 834 will clarifi this provision. Consistent with the earlier discussions aboutreleasing land under provisions of 10 CFR 834, LLW disposal facilities are not expected tobe released. and therefore. DOE is committed to retaining control of LLW disposal sites and[o continuing maintenance and monitoring activities as long as the land is under the controlof the Department. ”The 100-year inst imtional control period is to be used only in analysis asan assumption for when complete efficacy- of institutional controls may begin to erode. Thisapproach is consistent with that used for commercial LLW disposal.

Prox mi i~~’of Disuosa] Area to pro uertv Boundarv

DOE LLW disposal sites are typically located within large reservations. whilecommercial disposal sites are located on smaller plots of land with property lines that arerelatively close to the disposal area. The DOE requires in a performance assessment thatanalyses for transport of radionuclides in groundwater be conducted for a performanceboundan located 100 meters from the disposal facility. Therefore, if future DOE reservationboundaries are not significantly different than existing boundaries, DOE sites may have alevel of protection that is not accounted for compared to commercial sites. However, at ORRthe LLU- disposal site is less than 200 meters from the boundary of the reservation.Therefore, the large size of the DOE reservations alone does not always provide much greater

protection than do commercial sites.

.,*

Although larger buffer zones surrounding disposal facilities will generally providemore protection. the vadose zone typically provides greater delay in radionuclide migrationthan does the saturated zone. However, for humid sites like ORR, SRS, and Barnwell. thewater travel times in the saturated zones are comparable to those in the \’adose zone. and the

total water travel times are about 1 to 10 years. Sorption on environmental media. \vasteform performance. and engineered barriers generally pla} a larger role in overall protectionfrom radionuclide release at humid sites.

~ummae Qmruison of~OE and P. .

r]l’atel~’ ODerated Fac]lltles - Clo .surg. .

The NRC regulations require that closure plans be included in the license applicationfor a LLW disposal facility. These closure plans are used as the basis for development of theperformance assessment. While DOE has similar requirements for developing closure plans.it typically has not developed these plans, and assumptions about the final closure conditionsof the facility are contained in the performance assessments. This issue is being addressed inthe corrective action plans developed to resolve the vulnerabilities identified in the CWR.

Privately operated disposal facilities are located on land leased from a state or federal

government entity and must transfer lts operating license after all conditions of closure aremet, including a surety bond for potential future remedial activities. In addition, DOE mayaccept control of properly closed commercial disposal facilities if requested. Because DOEmanages its disposal facilities and controls the land used for disposal. the long-term controlof the land resides with DOE. In addition. as a government entity. DOE is required tosupplement the EIS governing its closure operation if there are substantial changes to the planor significant new circumstances.

.

21

. .4

Waste Forms

The primary purpose of waste forms for disposal of LLW is to provide stability forthe disposal facility, which will mmimize differential settlement resulting in breaches in thecover system and increased infiltration of water This condition is met at privately operated

and DOE-managed disposal facilities by the requirements for compressi~’e strength of thewaste or packaging material and minimized void space. Additional packaging is. required forClass B and C wastes to minimize releases and to decrease the potential for interaction withinadvertent intruders.

In humid to semi-arid environments, the waste form can play a significant role inhindering contaminant migration. In arid locations. waste forms do not play as crucial a rolem limmng contaminant migration because the hydroiogy of the site Itself prevents significantrelease and migration. In such cases. waste forms may still be importam in reducing the risk

by inadvertent intrusion by allowing the mtntder to recognize the waste as a hazard.Different waste forms have different leaching performance as well as different susceptibilityto environmental degradanon. Thus, the choice of waste form may be significant for someradionuclides m the overall performance of a disposal option.

This section provides a description of the waste forms accepted at the LLW disposalsites. a comparison of physical requirements for commercial and DOE waste. a scoping-levelcomparison of the performance of grout. polyethylene microencapsulation, and glass wasteforms. and an indication of which sites and which radionuclides may benefit from enhancedwaste forms.

Waste ForMs Accemed at J.T,W Disuosal Facilitie~

Barnwell has traditionally accepted cement-stabilized waste. However, new formssuch as vinyl ester styrene, vinyl chloride. and bitumen tie now being accepted (SCDHEC.1995). The Bamwell license requires that the leaching index of 6 or greater be met using theANS 16.1 test for all waste forms. The majority of the wastes being accepted at Barnwell areClass A LLW such as trash and dried solid material. Only a small percentage of the waste isdewatered ion-exchange resins, which have higher activities. High density polyethylenecontainers are accepted as high integrity containers.

“Envirocare of Utah accepts grouted waste forms. Envirocare has its own stabilizationfacility near the disposal site which can also use other types of stabilization agents.Macroencapsulated lead is accepted; lead bricks, lead shots, and lead blankets are allowed.At this time there are no environmental testing requirements for macroencapsulation. RockyFlats has sent macrc$encapsulated lead with 2 inches of low density polyethylene surrounding

..#

the waste. Microencapsulation using polyethylene is being investigated at Envirocare incooperation with Brookhaven National Laborato~. with an application in progress.Performance criteria have not yet been set for this waste form.

The DOE disposal sites also accept waste that has been stabilized using a variety ofstabilwzmon matrices. The primary considerations are stability of the lvaste form andmmim~zed void space.

Waste

#m extensive comparison of the physical requirements of commercial and DOE \vastehas been compiled by DOE (Cole et al.. 1995. Table C-1). The NRC limits free liquids

~<0.570 by volume or< 1?ZOvolume If within a high-integrity container) and void space incommercial waste. Class B and C waste must be stabilized to minimize contaminant releasesto the enwronrnent. and Class C waste must be in a form that minimizes intrusion. TheWaste Form Technical Position Document (NRC. 1991 ) provides guidance on other criteria

such as compression strength and resistance to radiation and biological effects.

DOE sites have physical requirements for waste that are similar to NRC requirements..All wastes must be stabilized. and requirements for free liquids are the same as those of theNRC at $JRS and Hanford (Cole et al.. 1995, Table C-1). Void spaces must be minimized. At

Oak Ridge, the waste forms must be stable in the presence of moisture and microbial activity.and must withstand internal factors such as radianon effects and chemical changes. AtHanford. the final process waste must satls~ performance criteria of the NRC (1991).

Perfm.mnce for Grout- Poknhvkne Micro ncap~d Glasse ui

Enhanced waste forms can be considered as a means of increasing the limitingconcentrations for certain radionuclides by reducing their leachability. To illustrate this point.scoping level estimates of the performance of grout. polyethylene microencapsulation. andvitrified glass waste forms at Hanford and SRS (SNL. 1996) are compared. Due to the

hydroscopic nature of Portland cement. radionuclides leaching from grouted wastes aremodeled assuming that the concentrations of radionuclides in the solid phase are inequilibrium with the concentrations in the liquid phase. Releases from polyethyleneencapsulated wastes are modeled using a diffusion process, with rates determined by thewaste loading; higher waste loadings result in higher diffusion rates. Releases from glass

waste forms appear to be limited by the dissolution rate of the glass; as the glass dissolves.the radionuclides near the outer. exposed surfaces are reIeased. Waste loading also affects

the dissolution and release rates for glass waste forms.

An estimate of relative retention performance for~hese waste forms normalized togrout performance is shown in Table 4. This relative retention performance assumes thatsufficient water is available to contact with the waste, implying disposal in more humidenvironments. Tc-99 is relatively poorly bound in grout, Cs- 137 is bound to a moderatedegree, and Pu-239 is tightly by the grout. The relative differences in performance of thedifferent waste forms reflect these conditions. For example. a glass waste form loaded at40V0 with wastes containing Tc-99 will perform about 390 times better than a grouted \vasteform loaded at 50?40:given equal initial concentrations of Tc-99 in the two wastes. theconcentration of Tc-99 in the leachate from the glass was~e form will be 390 times lower thanthat from the grouted waste form. Other values are interpreted slmilai-ly. “

Table 4. Relauve Retention Performance of Waste Forms Normalized to Grout Performance(from SNL. 1996).

I W-aste ‘

Waste Form LoadingRadionuclide

(%) Tc-99 CS-137 PU-239

10 39.000 4400 440Glass 30 3900 440 44

50 390 44 4.430 3200 370 37

Polyethylene 40 110 12 1.250 6 0.7 0.07

Grout 50 i 1 1

In general. the performance of the glass waste form is much better than that of the

polyethylene and grout waste forms, and lower loading rates result in lower release rates.However. glass tends to degrade more rapidly in high-pH conditions. so that the combinationof classified wastes in concrete vaults must, be evaluated carefully.

At lower loading rates, polyethylene performs better than grout for all threeradionuclides. although at higher loading rates, there is little benefit for Tc-99 and lessbenefit for Cs- 13.7and Pu-239. These differences reflect the relative strength of the chemicalbinding of the wastes with the cement in the grouted waste form relative to the physicalentrapment of wastes represented by the performance of the polyethylene waste foim.

Sites ~t Mavfifit F~ceci Waste Fo~

Because the interaction of the waste forms with water is necessary to cause releases ofradionuclides. sites located in the humid regions of the country stand to benefit most fromuse of enhanced waste forms. The disposal sites in the humid region of the country are ORR.

24\

,

SRS. and Barnwell. Oak Ridge uses a tumulus disposal facility. and SRS and Bamwell usevault facilities to reduce the infiltration of wa~er and minimize its contact with the waste.Because the infiltration rates in arid and semi-arid regions of the count~’ are low. the siteconditions tend to limit the release of radionuclides from LLW- disposal facilities. Therefore.enhanced waste forms do not provide significantly greater reduction in release ofradionuclides.

Kadionuclides that are highly-mobile and short-to ,moderately long-lived can benefitmost from enhanced waste forms because they are “retained in the disposal facility for longer .periods of time and are released at lower rates. However. shorter-lived radionuclides. that are ~no~ highly mobile in the environment (e.g., CO-60. Sr-90. Cs- 137) tend not to benefit great]!”from enhanced waste forms because they decay to low levels prior to reaching receptorlocations.

Longer-lived radionuclides tend not to benefit from enhanced w~aste forms as much asshorter-lived radionuclides because. like more-engineered @isposal facilities. the long-termperformance of waste forms is not known and conservative &sumptions are used to modelrelease over the longer times. Therefore, at some point in the future. the benefit of theenhanced waste forms is assumed to diminish, and the longer-lived radionuclides can migrateat higher rates.

Some radionuclides are not well suited to some waste forms. For example. the hightemperatures associated with the vitrification process used to make glass waste effectivelyprevent radionuclides with low volatility from being incorporated into the glass. Tritium andI-129 areexamples of volatile radionuclides that will not be entrained into glass. Tritiurn.C-14. Tc-99. and 1-129 release relatively easily from grouted waste without some type ofadded material to help bind them to the matrix.

Other radionuclides are well suited to some ~vaste forms. The high pH associatedwith grout results in formation of uranium compounds with low solttbility, so that aqueous

releases of uranium from grout are very low. This volubility-limited condition allows forhigher levels of uramum bearing wastes to be disposed of in grout.

Summw CQUM son of DOE and Prri ivatelv Oper ated Facilities - Waste Fot-m

The primary purpose of waste forms for LLW disposal is to provide stability to thedisposal facility. This stability is provided by specifying a minimum compressive strengththe waste form or waste package and by requiring that void space be minimized. Privatelyoperated and DOE-managed disposal facilities have similar requirements for waste form

.,*

stability. A wide range of waste matrices are ~ccepted by privatel}’ operated and DOE -managed disposal facilities. as long as the stability and leach requirements are met.

Disposal facilities in the humid regions of the country will benefit most fromenhanced waste forms because of the greater potential for water to infiltrate into the disposalfacility andcontact the waste. Barnwell. SRS. and ORR use more-engineered disposalfacilities to minimize the infiltration of water and subsequent contact with waste. Facilitiesin the arid region of the country do not benefit greatly from enhanced waste forms due to thelower amounts of infiltrating water.

.

The physical requirements for waste forms and the facilit} designs are smlilar forprivately operated and DOE-managed disposal facilities. Therefore. based on waste formcons] derauons. there appear to be no significant safety merits or demerits for using pri~’atel}operated facilities for disposal of DOE LLW.

performance Assessment

Performance assessments are intended to indicate whether a projected release ofradionuclides from a disposal site will meet certain radiological performance objectives forprotection of human health and the enwronrnent. Releases to water and the atmosphere andscenarios of inadvertent intrusion are considered. The performance assessments areconservative representanons of the actual processes occurring m nature. The followingsection compares concentration limits for DOE and private disposal facilities at arid sites .(NTS and Envirocare) and humid sites (SRS and Barnwell). The comparison also providesan indication of the relative conservatism of the performance assessments for the commercial .sites and the DOE sites. . .

Concentrate onsi

A comparison of contaminant concentration limits for wastes at arid and humid DOEand commercial sites is shown in Table 5. For Envirocare. SRS. and Bamwell. the limits arefrom their WAC: the limits listed in Bamwell’s WAC are the same as Class C limits. ForNTS, the limits are “action levels” being developed for the revised WAC. Action levels arenot limits on concentrations, rather they are being established to identify wastes that require cgreater levels of characterization and verification (DOE-JFO. 1996). For SRS. the limits are

from the W’AC for the E-Area vault for non-tritium. non-combustible wastes.

Table 5. Concentration Limits (pCifm; ) for Radioactive Constituents at Commercial andDOE Disposal Sites (assuming waste bulk density of 2.4 g/cm3)

Nuciide—

Arid Sites (Trench) Humid Sites (Vault)NTS Envirocare SRS Barnwell

Action Levelsa WAC WACb WACC

H-3 2E+I 1 ~ “ #E+06 j’E+()&

C-14 . 6E+03 1E+06 9E+c?3 8E+06

Sr-90 4E+07 , 5E+04 7E+08 7E+09Tc-99 3E+06 2E+04 2E+03 3E+06

Cs-137 9E+fJ6 1E+03 7E+08 5E+09

U-238 2E+06 7E+04 5E+04 e

Pu-239 6E+05 2E+03Am-24 1

7E+05 2E+055E+05 GE+(I3 4E+05 2E+05

~aterlevels of charactenzat!on and verlflcatlon, ActIon levels are not hm!ts on concentrations of radtonuchdes.

0 Based on Ctioackage hmlts m the E-Area Vault WAC and the volume of a B-25 box (96 ft3)

‘ Limits for Bamwell are for NRC class c wasted Limit for Class A waste, concentrations of H.3 are not Iim,ted for Cla55 c waste

“ NOconcentration limits in 10 CFR Part61

.

27

4

The concentration limits based on the Envirocare WAC (UDEQ. 1989) are lower thanthe action levels at NTS by two or more orders of magnitude for all radionuclides exceptC-14. For C-14. the NTS action level is lower than the Envirocare value by more than twoorders of magnitude; this difference is likely due to the difference in the approach used b!NRC and DOE in developing its intrusion scenario for that radionuclide,

The absence of site-specific limi[s for radionuclide concen~rations at NTS is based. inpart. on the results of the scientific studies supporting the draft performance assessment forthat site (e.g., Detty et al.. 1993 and Conrad; 1993). These studies provide evidence tosupport the assertion that there is no net downward migration of water in the vicinity of thedisposal site -- effectively eliminating groundwater as a migration pathway. Therefore. thereare no limits on inventories or concentrations of radionuclides based on releases \ogrounchvater .Additionally, because of the legacy of the weapons tests at the site. DOE plansIOmamtain long-term lnsututlonal control of the NTS. Waste management personnel at thesi~e indicate that this long-term institutional control. in combination with the extreme aridnature of the site and the practice of disposing of more highly contaminated waste at depthsup to 60 feet below the ground surface. results in a low probability for inadvertent intrusion.Therefore. limits based on intrusion are also not used at NTS. The upper limits onconcentrations of radionuclides at NTS are based on the definition of LLW, particularly the100 nCi/g limit related to TRU radionuclides.

The concentration limits based on the SRS WAC are similar to the Barnwell limits forSr-90. Cs- 137, Pu-239, and Am-241. The limits for tritium and Tc-99 at SRS are lower thanthe Iimlts a~Bamwell by more than two orders of magnitude; the lower values at SRS arelikely due to the high environmental mobility of these radionuclides, which results in limits .based on protection of groundwater. As with the arid sites, the lower limit for C-14 at SRS1s likely due to the difference in the approach used by NRC and DOE in developing itsintrusion scenario for that radionuclide.

Comparing the limiting concentrations of the four disposal facilities indicates theconsemausms.used in some of the analyses and highlights differences in disposal at arid andhumid sites. Because the analyses of the four facilities were done independently, differencesin the degree of conservatism used in the analyses can sometimes mask the differences due toactual site conditions. For example, the Envirocare facility in Utah has the lowest limits ofall sites for all indicator radionuclides except C-14 and Tc-99. For Pu-239 and Am-241,,,which are longer-lived radionuclides (Am-241 being limited by its long-lived progeny,Np-237) with moderate environmental mobility, the limits are about two orders of magnitudelower than at the other three sites. The arid conditions and remoteness of this site are moresimilar to NTS than SRS and Bamwell, so that the low limits for radionuclide concentrationsimply that a higher degree of conservatism was used in the development of the EnvirocareWAC. A primary source of this conservatism is probably due to assumptions made about the

characteristics of wastes received at the facility. Envirocare disposes primarily unpackagedLLW from D&D remedial action projects.

.

Because there are no site-specific limits on radionuclide concentrations at NITS [theaction levels result in administrative actions and not limits), this site can accept LLV’ withthe highest levels of radionuclides. The arid ciimate. procedures for bu~m~ wastes withhigher concentrauons of radionuclides at greater depths. and planned long-term institutionalcontrols at this site are the prim~ reasons for the absence of site-specific Iimlts at NTS.

At SRS and Bamwell in the humid southeast region of the country. the vault facilitydesigns result in relatively high limitmg concentrations for the shorter-litied radionuclides ‘(e.g.. H-3. Sr-90. and Cs-1 37). As discussed in the Design section of this report. more-engineered facilities like the vault can retain these shorter-lived radionuclides until they “ -decay to low levels. effectively resulting in higher limits.

Summ arv Co-son of DOE and Privately Operate d FacIlltles - Performance Assessmeu. . .

The disposal facility at the NTS, located in the arid region of the country, has no site-specific limits on concentrations of radionuclides in LLW;. the limits are based on theregulatory definition of LLW, pamcularly related to TRU radionuclides. In supporting theselimits. NTS takes credit for its arid environment and resulting absence of a groundwater

.pathway. the planned long-term institutional controls of the site based on the legacy of itsformer mission. and its practice of burying highly contaminated wastes at depths of up to 60feet. The absence of site-specific limits at the NTS illustrates the benefits of arid sites fordisposal of LLW.

The Envirocare disposal facility in Utah, which has climatic and hydrologic attributessimilar to the NTS, has relatively restrictive limits for radionuclide concentrations that are inthe range of NRC’s Class A waste. Because it has an arid climate more similar to NTS thanSRS and Bamwell. these lower limits appear to result more the type of wastes being disposedrather than. from site-specific performance. Therefore. from a safety standpoint based onperformance assessment. if concentrations. of radionuclides meet the Envirocare WAC,disposal of DOE LLW at Envifocare should not be of concern.

Barnwell and SRS are located near each other in the same climatic region and insimilar geologic environments. Both sites use vault disposal facility designs. At SRS, theconcentration limits for radionuclides are based largely on the site-specific performanceassessment, which establishes limits based on releases to groundwater and the atmosphere,and on protection of inadvertent intruders. The concentration limits for Bamwell are theNRC Class C limits, which were based primarily on scenarios of inadvertent intrusion intogeneric facilities. For most radionuclides. the concentration limits for SRS and Bamwell aresimilar. However, for the radionuclides that are more mobile in the environment (e.g.,

tritiurn and Tc-99), the limits at SRS based on releases to groundwater are more restrictivethan Bamwell for these radionuclides.

29

While the disposal facilities located in arid environments are capable of disposing ofLLW with higher concentrations of all radionuclides. the Envirocare WAC illustrates thatthis capability is not always used. However. as both Bamwell and SRS illustrate. disposalsites in the humid region of the country that use more engineered facilities can dispose ofrelatively high levels of shorter-lived radionuclides. While sites in arid regions can. ingeneral. dispose of LLW with higher concentrations of radionuclides than can sites in humidregions. the performance assessment for each site results .in a site-specific WAC that accountsfor these differences. Therefore. as long as the site-specific WACS are met. there appear to ,.be no significant safety merits or demerits based on performance asiessmems from disposingof DOE LLW at facilities in humid or arid environments. ● .,

..4

Approval and Oversight

In this section. the approaches used by NRC or the Agreement States and DOE toobtain approval for disposal facility operanons and to maintain oversight of those facilities ispresented. The differences in the approaches related to safety Issues are highlighted.

moach Used tw NRC and Aereeme nt States

To obtain a license from NRC or an Agreement State for a facilit] to dispose of LLW.an applicant must comply with the requirements of 10 CFR Part61. An application must besubmitted prior to construction of the disposal facility. This application must contain. inaddition to general information, the results of the site selection process. results of a detailedinvestigation of the site characterization. and an analysis of performance of the site. The

license application is reviewed by the NRC or Agreement State and if approved, a license isissued and disposal operations can commence. Prior to licensing, financial assurances arerequired of the applicant to ensure that all phases of disposal facility activities. includingmonitoring and any required maintenance during the institutional control period will befunded.

The land on which the site is located must be owned by the State or Federalgovernment and leased to the operator. This requirement is to ensure the long-term control ofthe land after the site is closed. The site must be operated in accordance with Part 61 and anyadditional requirements listed in the license. Periodic license renewal is required. Theoperating history of the facility is reviewed at that time and a decision is made to eitherpermit or deny continued operations. Ongoing compliance is maintained through reviewsand inspections of waste generator operations, and by inspections and audits of the disposal

- facility operations; these are both conducted by the NRC or the Agreement State regulatoryagency.

When the operations phase is completed. the license is amended to indicate the siteclosure phase. In addition to decommissioning activities, the licensee is required to maintainpost-closure monitoring activities for 5 years to ensure that the site is stable and ready to beturned over for institutional control. A longer or shorter period may be set if conditions

warrant. After the NRC or Agreement State finds that the disposal site closure is satisfactory.it transfers the license to the State or Federal government entity that owns the site. If theDOE owns the site. the license is terminated because NRC lacks regulatory authority overDOE for this activity.

DOE LLW disposal facilities are required to submit site-specific radiologicalperformance assessments demonstrating compliance with Order 5820.2A performance

31

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objectives to DOE headquarters for review and approval. A Peer Review Panel (PRP).,established by DOE headquarters; of experts in the fields of performance assessment. healthphysics, modeling, and hydrogeologic processes, reviews the performance assessment andother appropriate documentation for techmcal adequacy. The performance assessment. thefindings of the PRP, and other documentation are then reviewed by DOE headquarters staff.and a decision on the acceptance of the performance assessment is made by the Assi’stamSecretary for Enwronmental Management

. .

“ LLW disposal facilities are also required to submit compo3ite analyses accounting for .all sources of radioactive material that may exist in the ground at a DOE site that ma~contribute to the dose projected to a hypothetical member 6f the public from an active orplanned LL W disposal facility. The composite analysis and other appropriate documentationare reviewed by DOE headquarters staff. and a decision on its acceptance is made by theAssistant Secretary for Environmental Management.

Upon acceptance of these two analyses, DOE headquarters issues a DisposalAuthorization Statement (DAS). The DAS sets forth the conditions for approval of theperformance assessment and the composite analysis, and the conditions for the design.construction. and operation of the LLW disposal facility to provide a reasonable expectationof compliance with the performance objectives of Order 5820.2A and considering the resultsof the composite analysis or any other required assessments or documentation. The DASfictions similar to a license issued for the commercial disposal facilities.

DOE is responsible for oversight and compliance reviews and appraisals at itsdisposal facilities, and these are conducted by the Office of Environment, Safety, and Health.which is a separate office within DOE from the Office of Environmental Management, whichhas program responsibility over the LLW disposal facilities. As part of its programmaticresponsibilities and in reference to DNFSB recommendation 94-2. EM completed avulnerability assessment of each disposal sne and of the LLW system as a whole (DOE1996c). -

on of DOE and Privat elv O~erated Facilities - Apmo ~h~val and Oversi

Privately operated LLW disposal facilities are required to obtain a license prior tooperation, to undergo compliance reviews and appraisals, and to receive approval andtransfer of license after the facility is closed. The license and approvals are granted by anexternal, independent government organization, either the NRC or the Agreement State, withno ties to the operational aspect of the facility.

DOE LLW disposal facilities are now required to obtain a disposal authorization

statement (for new facilities prior to operation) and to undergo compliance reviews andappraisals. The authorization to operate will be granted by the same office that is in charge

of all other aspects of the disposal facility.

..b.

The compliance reviews and appraisals areconducted m~emally within DOE. but by another of~ce. Past weaknesses inherent in DOE”sinternal review and approval ”methods have been identified through the DNFSBRecommendation 94-2 and are being resolved. Improvements described in the 94-2Implementation Plan in the Radiological Assessment tasks for approvals of the faci~ityperformance assessments and composite analyses and in the Regulatory Structure andProcess task area for a revised Radioactive Waste Management Order chapter on LL U: willresult in improved approval and oversight of DOE LLW disposal.

Except for the differences in the relationship between the operator and regulator of -disposal facilities (i.e.. privately operated facilities are regulated by external. independent. ‘government agencies and DOE disposal is self-regulated), the requirements for both are -similar. Therefore. there appear to be no significant safety merits or demerits from usingprivately operated facilities for disposal of DOE LLW.

,,. .

4

CONCLUSIONS

One of the tasks delineated by the Defense Nuclear Facilit~ Safety Board in itsRecommendation 94-2 was an evaluation of privately operated facilities for disposal of DOELLW. The safety merits and demerits of using private disposal facilities compared todisposing of LLW at DOE facilities have been evaluated based on se~~enfunctional areas:siting. design, operations. closure. waste form. performance assessment. and approval andoversight.

The specific requirements and practices for privately operated and DOE-operatedfacilities often differ within these functional areas. primarily due to the difference inrequirements of the NRC or Agreement State and DOE. The NRC de~’eloped regulations toapply to commercial waste generators that are distinct entities from those that dispose ofLLW. and the type of waste generated m the commercial sector is generally similar from siteto sne. The disposal practices for DOE LLW developed from on-site disposal of wasteswhere closer relationships existed between generators and disposers and the need for a formal

interface was less obvious. In addition. the varied types of waste generated by the DOEfacilities related to weapons development and energy research did not lend itself to a generalclassification system.

Although there are differences in implementation between the NRC and DOE forthese seven functional areas. the resulting level of protection provided by the aggregate ofthese seven functional areas are similar for both systems. This similarity is not surprisingbecause NRC and DOE evolved from the same parent organization and have continued closecommunication about waste disposal and the DOE national laboratories were usedextensively by NRC to develop the technical basis for its LLW disposal regulations.

While m general the NRC and DOE approaches result in similar levels of protection.in practice two differences are worth noting. First, the concentration limits at Barnwell forhighly mobile radionuclides (e.g., tritiurn and Tc-99), which are based on the NRC Class Climits, are two and three orders of magmtude,highert han.at the Savaimah River Site. Thedisposal facilities at both sites are vaults, and the primary difference appears to be thedifference: in conservatism used in the analysis of releases to groundwater. Second. the self-regulation of DOE has, in the past, resulted in some requirements of DOE Orders not beingimplemented. For example, the requirement for the development of closure plans was notbeing complied by the all of the DOE sites; this deficiency is now being addressed by thecorrective action plans for the complex-wide review as identified in Revision 1 of theImplementation Plan for Recommendation 94-2.

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Conrad. Stephen H., 1993. “Using Envlronrnental Tracers to Estimate Recharge through anArid Basin.”’ presented at 1993 International High-Level Radioactive Waste ManagementConference. Las Vegas. NV. .April 26-30.1993.

Deny. T.E.. D.P. Hammerrneister. D.O. Blout. “M.J. Sully, R.L. Dodge, J. Chapman. and “S.W. Tyler.1993. “Water Fluxes in a Deep Arid-Region Vadose Zone.” Abstract inProceedings of the 1993 Fall .Meenng, Amcrlcan Geophysical Union. Supplement ToEos. October 26.1993.

DOE (Department of Energy), 1988. “’Low-Level Waste.” Chapter 111in Radioactive Waste “Management. Order 5820.2A..

DOE (Department of Energy), 1996a. “Performance Evaluation of the Technical Capabilitiesof DOE Sites for Disposal of Mixed Low-Level Waste.” DOE/ID-10521. SAND96-0721.3 Volumes. March, 1996.

DOE (Department of Energy), 1996b. Implementation Plan: Defense Nuclear FacilitiesSafety Board Recommendation 94-2. Rev. 1, U.S. Department of Energy. April.

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DOE-NTFO. 1996. “Nevada Tes~ Site Defense Waste Acceptance Criteria. Certification, andTransfer Requirements,” NVO-325. Rev. 1. Prepared by the U.S. Department of EnergyNevada Field Office and Reynolds Electrical & Engineering Co., Inc., WasteManagement Department. September. 1996.

INEL (Idaho National Engineering Laboratory), 1994. “Directions in Low-LevelRadioactive Waste Management: A Brief History of Commercial Low-Level RadioactiveWaste Disposal,” DOE.LLW-1 05, Rev, 1. August, 1994.

Maiieras. S. J.. A. S. Rood. S. O. .Magnuson, IM. E. Sussman. and R. N. Bhatt. 1994.“Radioactive Waste Management Complex Low-Level Waste Radiological PerformanceAssessment,” EGG-WM-8773. Idaho Falls, ID: U.S. Department of Energy Office ofEnvironmental Restoration and Waste Management, DOE Idaho Operations Office.

MMES (Martin Marietta Energy ‘Systems), EG&G Idaho, Inc. and Westinghouse SavannahRiver Company. 1994. “Radiological Performance Assessment for the E-Area VaultsDisposal Facility,”” WSRC-RP-94-2 18, Rev. O. Aiken~ SC: Westinghouse SavannahRiver Company.

Newbe~. M;.. 1994. “-Comparative Approaches to Siting Low-Level Radioactive U;aste

Disposal Facilities,” DOE-LLW- 199, Idaho National Engineering Laborato~’. EG&GIdaho. Inc.. July

NRC (xuclear Regulato~ Commission). 1982. “Final Environmental Impact Statement on10 CFR Part 61 Licensing Requirements for Land Disposal of Radioactive W-aste.”NUREG-0945. Office of Nuclear lMaterial Safety and Safeguards. U.S. NuclearRegulatory Commission, November.

NRC (Nuclear Regulatory Commission). 1991. “Waste Form Technical Position. Revision1.“ Prepared by Technical Branch. Division of Low-.Level, Waste Management andDecommissioning. Jan. 1991.

Oreskes. NT..K. Shrader-Frechette, and K. Belitz, 1994. “Verification, Validation. andConfirmation of Numerical Models in the Earth Sciences,” Science. 263,641-646.

ORNL (Oak Ridge National Laboratory), 1994. “Performance Assessment for the‘ Continuing and Future Operations at Solid Waste Storage Area 6,” ORNL-6783. Oak

Ridge. TN: U.S. “Department of Energy. Oak Ridge National Laboratory.

Shott. G.J.. C.J. Muller. L.E. Barker. D.E. Cawlfield. F.T. Lindstrom. D.G. Linkenheil. M.J.Sun}. L. .McDowell-Boyer. and D.J. Theme. 1996. “Performance Assessment for theArea 5 Radioactive Wai+te Management Site at the Nevada Test Site. Nye County,Nevada,” DOE/NV/l 1432-196. Revision 3, August, 1996.

SNL (Sandia National Laboratories), 1996. “Waste Form Performance Assessment Task,”TTPAL2-6-TI-012. Draft Letter Report. Sandia National Laboratories. July. 1996.

SCDHEC. (South Carolina Department of Health and Environmental Control). 1995.Radioactive Material License to Chem-Nuclear Systems, Inc., Barnwell WasteManagement Facility. License number 097. Amendment 46. August 11.

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